PSExec Pass the Hash

The psexec module is often used by penetration testers to obtain access to a given system that you already know the credentials for. It was written by sysinternals and has been integrated within the framework. Often as penetration testers, we successfully gain access to a system through some exploit, use meterpreter to grab the passwords or other methods like fgdump, pwdump, or cachedump and then utilize rainbowtables to crack those hash values.

We also have other options like pass the hash through tools like iam.exe. One great method with psexec in metasploit is it allows you to enter the password itself, or you can simply just specify the hash values, no need to crack to gain access to the system. Let’s think deeply about how we can utilize this attack to further penetrate a network. Lets first say we compromise a system that has an administrator password on the system, we don’t need to crack it because psexec allows us to utilize just the hash values, that administrator account is the same on every account within the domain infrastructure. We can now go from system to system without ever having to worry about cracking the password. One important thing to note on this is that if NTLM is only available (for example its a 15+ character password or through GPO they specify NTLM response only), simply replace the ****NOPASSWORD**** with 32 0’s for example:

******NOPASSWORD*******:8846f7eaee8fb117ad06bdd830b7586c

Would be replaced by:

00000000000000000000000000000000:8846f7eaee8fb117ad06bdd830b7586c

While testing this in your lab, you may encounter the following error even though you are using the correct credentials:

STATUS_ACCESS_DENIED (Command=117 WordCount=0)

This can be remedied by navigating to the registry key, “HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanManServer\Parameters” on the target systems and setting the value of “RequireSecuritySignature” to “0”.

That is it! We successfully connect to a seperate computer with the same credentials without having to worry about rainbowtables or cracking the password. Special thanks to Chris Gates for the documentation on this.